Now to the ebola emergency. The second American aid worker infected begins her journey home today. As her colleague is getting better under close supervision. Steve osunsami is at Emory hospital where they will be treated. Good morning. Reporter: That second is expected to leave Liberia this evening our time and arrive here tomorrow mid-morning. The world is waiting for Nancy writebol to return. Soon to become the second person ever to carry the ebola virus on to U.S. Soil. On Saturday, her colleague, Dr. Kent Brantly was the first. That's him in a full biohazard suit, walking into the hospital. To see him walk, which hadn't even occurred to me, was just unbelievable. Reporter: His wife, amber, not allowed to hold his hand, but saw him. Flying him from Africa was complicated to say the least. He was moved in a specially-designed isolation pod like this one, and an airtight tent good for one patient at a time. Which is why they are making two trips. Today writebol will travel to bangor, Maine, before landing at Dobb bins air force base outside of Atlanta Tuesday afternoon. We have the expertise to safely care for these patients. Reporter: They contracted the disease treating african patients. The CDC next door is on alert, taking every precaution, confident they can keep the staff healthy and the disease from spreading. The bottom line is we know how to stop it. Reporter: This has been quite a local story as well. The families here concerned that such a deadly pathogen being brought in. But those fears misplaced, the CDC just down the street has much more deadly bugs safely on lockdown. And joined by a professor of medicine and Dr. Rich Besser. We heard Steve osunsami talk about the anxiety in Atlanta. Are you facing any kind of a brushback from patients or families at the hospital concerned this could spread? We have been hearing some concern about safety, and frankly we view that as an opportunity for education. And rich Besser, we heard from Dr. Brantly's wife that his condition is improving. And he received an experimental see rum before he left Africa. What can you tell us about that? There was discussion about one dose of an experimental serum coming, and he said to give it to his colleague. We don't know if this is the same, we don't know what exactly it was. Look at it closely, because as you know, there's no known drug treatment or cure for ebola. And patients can seem to be improving and slip back. When will we know when someone is safe to go out in public? Yeah, they will be monitoring him closely. What's normally seen in a case of ebola, you have the acute symptoms, you are so sick, and patients who are going die, it's a downward spiral towards death. Usually not able to a walk and slip back. I'm sure they'll monitor his liver and kidney function. They tend to get hit hard. I have talked to people who have treated ebola patients, but over the acute illness, they are able to go home, and no family members pick it up from the ex exposu exposure. The body learns to fight the infection. That's what you're looking for. Since there's no drug, the immune system has to fight that. The signs are promising, and he is improving. Also promising that his colleague is well or stable enough to travel to the united States. They are going to have to assess her again, the journey can be ardous. The team will have to do the assessment. Can she make the journey back to Atlanta? Thank you both very much.

This transcript has been automatically generated and may not be 100% accurate.

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